fix issue where student weightable pass/fail point_totals were not being rescued on the assignment model.
fix issue where student weightable pass/fail point_totals were not being rescued on the assignment model.

UM-USElab/gradecraft-development,peterkshultz/gradecraft-development,UM-USElab/gradecraft-development,peterkshultz/gradecraft-development,UM-USElab/gradecraft-development,mkoon/gradecraft-development,peterkshultz/gradecraft-development,mkoon/gradecraft-development,mkoon/gradecraft-development,UM-USElab/gradecraft-development